Thermoelastic sulfonated polymers have been described in a number of U.S. patents. These sulfonated polymers are derived from polymeric materials having olefinic unsaturation, especially elastomeric polymers such as butyl and EPDM rubbers. U.S. Pat. No. 3,642,728, herein incorporated by reference, clearly teaches a method of selective sulfonation of olefinic unsaturation sites of an elastomeric polymer to form an acid form of a sulfonated elastomeric polymer. The olefinic sites of the elastomeric polymer are sulfonated by means of a complex of a sulfur trioxide donor and a Lewis base. The SO.sub.3 H groups of the sulfonated elastomer can be readily neutralized with a basic material to form an ionically cross-linked elastomer having substantially improved physical properties over an unsulfonated elastomer at room temperature. However, these ionically cross-linked elastomers may be processed like a conventional thermoplastic at elevated temperatures under a shear force in the presence of selected preferential plasticizers which dissipate the ionic associations at elevated temperatures, thereby creating a reprocessable elastomer.
The basic materials used as neutralizing agents are selected from organic amines or basic materials selected from Groups I, II, III, IV, V, VI-B, VII-B, and VIII and mixtures thereof of the Periodic Table of Elements. Although these sulfonated elastomeric polymers prepared by the process of this patent are readily useable in a certain number of limited applications, they are not as readily adaptable for the manufacture of an extrudable and injection moldable elastomeric article as are the improved compositions of the present invention, wherein both improved physical and rheological properties are realized.
U.S. Pat. No. 3,836,511, herein incorporated by reference, teaches an improved process for the sulfonation of the olefinic sites of the elastomeric polymer, wherein the improved sulfonating agent is selected from acetyl sulfate, propionyl sulfate and butyryl sulfate. The neutralizing agents employed to neutralize the acid form of the sulfonated elastomeric polymers are organic amines. The resultant ionically cross-linked sulfonated elastomers prepared by this process do not exhibit both the improved physical and rheological properties of the compositions of the present invention.
U.S. Pat. No. 3,870,841, herein incorporated by reference, teaches a method of plasticization of the polymeric backbone of a neutralized sulfonated plastic polymer by means of a polymer chain plasticizer which is a liquid compound having a boiling point of at least about 120.degree. F. The polymer chain plasticizer is selected from a dialkyl phthalate, a process oil or an organic acid ester. Additionally, a domain plasticizer can be incorporated into the composition, wherein the domain plasticizer reversibly disrupts the association of the sulfonated groups at a temperature of forming. The compositions formed by this process are not suitable for the manufacture of high performance elastomeric articles formed by extrusion or injection molding processes, as are the compositions of the present invention.
U.S. Pat. No. 3,847,854, herein incorporated by reference, teaches a method of improving the processability of neutralized sulfonated elastomeric polymers by the addition of a preferential plasticizer which has at least one functional constituent which exhibits a bond moment whose absolute value is at least 0.6 Debyes, and must be a liquid at the desired processing temperature of the neutralized sulfonated elastomeric polymer. Again, the composition of the present invention are more adaptable for use in the manufacture of high performance elastomeric articles.
Products resulting from the aforementioned methods for obtaining neutralized sulfonated elastomeric compositions possess either unsuitable rheological or physical properties for the applications envisioned in the present invention.
For example, the physical properties of the resultant sulfonated elastomeric products of these aforementioned patents are unsuitable for a major application of an extrusion process, namely the manufacture of garden hose, wherein excellent resilience, dimensional stability, excellent low and high temperature flexibility, excellent flex fatigue, and excellent coilability are needed. Furthermore, the high melt viscosity and melt elasticity of these materials makes extrusion or injection molding difficult, if not impossible. These materials of the aforementioned patents which are generally processable by only compression molding have unsuitable physical properties for this major application of elastomeric hose articles.
The materials cost of the compositions of the instant invention is substantially reduced over those of the aforementioned patents, wherein these previous patents failed to realize the criticality of the proper selection of the chemical and physical uniqueness of the basic elastomeric backbone, the degree of sulfonation, the proper selection of neutralizing agent in conjunction with plasticization, and the ability to extend these sulfonated polymers with oils and fillers. Unsulfonated elastomers, when extended with oils and fillers, show a general deterioration in physical and rheological properties, as is clearly shown in the Detailed Description of the present invention. Quite suprisingly, through the proper selection of oil and filler within a critical ratio of filler to oil, the sulfonated elastomeric composition of the present invention shows a marked improvement in both rheological and physical properties.
U.S. Pat. Nos. 3,974,240 and 3,974,241, filed on Nov. 18, 1974, describe the blending of a crystalline polyolefinic material with a neutralized sulfonated elastomeric polymer in an attempt to improve both the rheological and physical properties of the elastomeric polymer. The selection of the use of the crystalline polyolefinic material to improve both the stiffness and the melt viscosity of the composition, based in part upon the limitation of the use of fillers, such as carbon black, clays, calcium carbonate or silicates, as a single additive to the elastomeric polymer.
U.S. Pat. Nos. 4,160,751 and 4,169,820, which are incorporated herein by reference, teach thermoplastic compositions of sulfonated EPDM terpolymer. The thermoelastic compositions of the instant invention show improved mechanical properties over the compositions of these patents due to the high molecular weight of the instant sulfonated polymers.
The present invention teaches unique and novel compositions of matter for producing a high performance elastomeric article by an extrusion or injection molding process, wherein the compositions of the elastomeric article have a viscosity of 0.73 sec.sup.-1 at 200.degree. C. of about 8.times.10.sup.4 to about 8.times.10.sup.6, and a Shore A Hardness of about 50 to 95.
The instant invention describes a class of compounds based on the sulfonated ethylene-hexene-1 or ethylene-octene-1 terpolymers which can be processed on plastics type fabrication equipment at high rates and which possess improved physical characteristics, such as low temperature flexibility and rubbery feel. One of the essential aspects of the present invention is that only a restricted class of the subject sulfonated elastomers may be readily employed for extrusion fabrication. The restrictions are primarily associated with processing and product performance characteristics. These characteristics are to a degree modulated by the type and concentration of various compounding ingredients. The compositions of the instant invention will, therefore, involve a class of compositions based on a restrictive class of sulfonated elastomers.
A substantial segment of the plastics and rubber fabrication industry employs a fabrication technique known as extrusion to form articles which can be classified as sheet, profiles, tubing and film. The applications employing these fabrication techniques, such as windshield wipers, weather stripping, refrigerator door seals, garden hose, etc., require materials which are flexible and tough. Two broad classifications of materials which have been used are vulcanized elastomers and plasticized thermoplastics, such as polyvinyl chloride (PVC). The fabrication of extrusion articles based on vulcanized elastomers is a major item of cost involving the vulcanization procedure. Not only is this step costly from an energy intensive viewpoint, but it is time consuming. The use of plasticating extrusion for thermoplastic materials is more economical and results in high exstrusion rates for materials such as plasticized PVC. While these materials possess a degree of flexibility, they do not have a good rubbery feel or good low temperature flexibility. It is, therefore, desirable to have materials which can be processed on plastics type fabrication equipment at conventional plastics rates and which possess the flexibility and subjective rubbery characteristics of vulcanized elastomers.